1. Special computer-based languages
and graphics based tools that allow a designer to design at a
less detailed level; the tool takes care of the detail.

3. Libraries of programs and circuits
that can be reused.

EE Goes Soft

As circuits and computers get
more complex, design and hardware engineers turn even more to
information technology to do their work. Through the use of languages,
such as VHDL, engineers can build soft prototypes to check their
logic instead of using hardware prototypes. This saves time and
money. Virginia Tech was the first university to teach undergraduate
and graduate students VHDL.

Either VHDL code, or high-level graphics-based design
tools (bottom ) can be used to generate gate diagrams (top).

"EE is in the middle of a revolution," he said.
"Fewer people are designing detailed hardware, and more
are moving to software. Within the next five to 10 years, engineers
will sit at a computer, write a program to design their hardware
and check it out, then use a software tool to synthesize the
design," he explained. "We're moving to full automation."

VHDL, a digital hardware description language, has been particularly
powerful in this revolution. VHDL is a computer language that
enables engineers to develop soft prototypes.

"With VHDL we can describe the computer we want to build,
then simulate it by putting in our inputs and outputs and seeing
if it does the right thing. Then we feed the description into
a synthesis tool that automatically develops the circuit and
gives us a gate diagram. At present, we can't design an entire
large computer that way, but we do it in chunks, then connect
the chunks manually," Armstrong said.

"VHDL is a way to describe a computer system without
getting lost in the details. We used to draw these gates on paper
or on the computer, but with up to 20,000 gates, it is easy to
lose perspective. Now we create high-level models and analyze
them."

Reconstructing Old Components

The language is not used only for designing new hardware,
but sometimes for reconstructing old components. For example,
the U.S. Department of Defense has used some parts for more than
40 years. "Originally these parts may have been made with
vacuum tubes, then integrated circuits," Armstrong said.
"Instead of trying to recreate the obsolete technology,
which can be very difficult and expensive, we can describe the
part in VHDL. This then becomes the documentation and part description,
from which a synthesizer tool can design a state-of-the-art replacement."

VHDL models used for design can also be used to generate testing
programs. Testing complex systems is as complicated as designing
them. VISC researchers have been involved with developing VHDL-based
tests for the DARPA Rapid Prototyping of Application-Specific
Signal Processors (RASSP) program. The RASSP program involves
developing equipment from off-the-shelf technology that can be
updated through periodic upgrades. "In this case, we're
using VHDL to recreate existing equipment," Armstrong commented.

VHDL was developed 10 years ago from a government program
desiring six different contractors to be able to communicate
their specifications. "After that, the IEEE took over the
language and developed the standards that we use today."

Educational Leaders

Armstrong was on the IEEE standards committee, and along with
Professor Gail
Gray, has been instrumental in Virginia Tech becoming the
first university to teach the language.

"This is a case of research being directly carried into
the classroom," he said. "We were the first to teach
it at either the graduate or undergraduate levels. We have educated
more students in VHDL than any other place in the world.

"Our students don't learn the whole language, but use
it as a CAD tool. They make models of little designs, simulate
them, and check them out," he explained. "We also have
them translate VHDL manually into a circuit so they can see how
it works and so they can understand the automatic tools. Our
undergraduates also take VHDL and synthesize field programmable
gate array (FPGA) circuits."

Does the "softening" of electrical and computer
engineering change what students should learn? "We need
to teach the fundamentals, so that they can understand these
systems. But maybe, when we teach fundamental circuits, we can
also teach the design tools.

"The new engineers will write programs to design their
hardware. We need to teach more software to our hardware engineers."

See Also:

Modeler's
Assistant - The Modeler's Assistant (MODAS) is an interactive
graphics system that enables rapid development and test and VHDL
models. MODAS relieves the the modeler of much of the burden
of developing behavioral models and enforces a structured approach
to modeling.

RASSP
- VISC researchers are working with the Research Triangle Institute
to develop two tools, the VHDL Test Bench Generator and the Signal
Processing Algorithm Library, as part of the RASSP project.